(This time) first day of This month: $date = new DateTime('first day of this month');(This time) last day of This month: $date = new DateTime('last day of this month');

In this month:$firstDayThisMonth = new DateTime('first day of this month');$firstDayThisMonth->setTime(0, 0, 0);$firstDayNextMonth = new DateTime('first day of next month');$firstDayNextMonth->setTime(0, 0, 0);